The invention relates to apparatus driven by pumps, e.g., membrane-based gas separation apparatus.
Membrane-based air separation involves flowing air in a feed channel of a membrane cartridge past one side of a membrane that preferentially passes oxygen over nitrogen through the membrane to a permeant channel in the cartridge on the other side of the membrane. Nitrogen enriched air is removed from the feed channel, and oxygen enriched air is removed from the permeant channel. In a pressurized mode of operation of such separation, a single pump is used to provide compressed air to the feed channel, and oxygen enriched air passes through the membrane to the permeant channel, which is at atmospheric pressure. In a vacuum mode of operation, one pump is again used to provide compressed air to the feed channel (though at a lower pressure than in the pressurized mode), and, in addition, a second pump is used to pull a vacuum in the channel, as is described in Gollan, A. and Kleper, M. H., "Membrane-Based Air Separation"Symposium Series, 250, Vol. 82, pp. 35-47, 1986, which is hereby incorporated by reference.